Whizlabs decide to enhance their code quality checks. They integrated SonarCloud with their pipeline. 
What should they do for preventing pull requests on a master branch if code quality check fails?

Answer options:

A.In Azure DevOps Repo for master branch set "Add status policy" for SonarCloud quality gate to Required
B.In SonarCloud on Administration panel set Provider Key to Azure DevOps Services
C.In SonarCloud on Quality Gates create a new Gate with the condition when Quality Gate fails
D.In Azure DevOps Pipeline for Build solution task input Custom Conditions in Control Options Settings

Correct Answers:A 
To reject a pull request on the master branch, you need to open Project Settings in DevOps and on Repos/Repositories panel select master branch. The Build Validation option should be enabled. On the Status Check subpanel, select the "+" sign to add a new status policy. 

From the dropdown, select "SonarCloud/quality gate", Required option, and click Save.

After these settings, any pull request for the master branch will be rejected if the code quality gate fails. 
All other answers are irrelevant to this problem. 
For more information about integration with SonarCloud and quality gates, please visit the below URL- 

https://azuredevopslabs.com/labs/vstsextend/sonarcloud/